Document dispensers are well known and have been used in a variety of document handling applications with great commercial success over the years. Generally, such dispensers are used to handle sheet-like materials such as papers, envelopes, catalogues, credit cards, business cards, and other similar items.
In practice, the document dispensers are typically used in connection with various types of document processing systems, such as printers, folding machines for properly folding the printed materials, laminators, accumulating machines for properly arranging the customized printed document or documents with all of the insert materials, inserting machines for inserting the collations into envelopes, labellers, mailing machines which close and seal the flaps of the envelopes, and print a postage indicia thereon, and sorters for sorting out the printed envelopes. Often, the document dispensers are used as the front side of a fully automatic system.
In a typical arrangement of a document processing systems, there may be a stack of documents loaded onto a loading end of a document dispenser. The documents are generally stacked in a vertical manner with each of the documents lying in a horizontal plane. When the dispenser is in operation, a separating mechanism typically first separates the document from the stack, and then the document passes through a feeding mechanism which feeds the separated document into another apparatus for further processing. There are two common designs of dispensers which are available in the existing market. There are bottom feed dispensers and top feed dispensers. In a bottom feed dispenser, the document is removed from the bottom of the stack and then fed into the feeding portion of the dispenser. In a top feed dispenser, on the other hand, the document is removed from the top of the stack and then fed into the feeding portion of the dispenser. Furthermore, depending on the type of document being dispensed by the document dispenser, the dispenser may utilize friction rollers, reciprocating friction pusher feed elements, vacuum lift, vacuum pusher feed elements, grippers, or clamp type devices.
Generally, a desirable characteristic of the document dispenser is the capability of handling a large through-put at a high rate of speed so as to optimize the costs of the manufacturing and the maintenance of the various components of the dispenser. However, as in many document dispensers of this type, the dispensers are susceptible to paper jams, double feeds, and other unacceptable conditions if a wide range of documents of varying thicknesses are fed into the dispenser. In many instances, the dispenser needs to be adjusted each time when documents of different thicknesses are fed into the dispenser, thus leading to down-time of the dispenser.
In U.S. Pat. No. 5,498,123 issued to ALICEA on Mar. 12, 1996, a bottom feeding mechanism is taught. In particular, the mechanism is used for feeding media only one piece at a time to a functional unit, such as a printer. The bottom feeding mechanism comprises a feed roller assembly and a conveyor belt assembly functioning as a first stage gate and a set of snubber rollers functioning as a second stage gate. The feed roller and the conveyor belt can only move unidirectionally, which are controlled by a driving means through one-way clutches. Further, each snubber roller is independently driven. When a medium is fed to hit the gate, vertical component of momentum of the feeding mechanism forces the conveyor belt deflecting the leading edge and opens up the gap to its proper opening to allow one piece of media to pass through. Should more than one piece pass through the first stage gate, the second stage gate will virtually eliminate the possibility of more than one piece passing through this gate.
In U.S. Pat. No. 5,888,047 issued Mar. 30, 1999 to AUERBACH et al., a separating and feeding machine for bound booklets is taught. The separating and feeding machine is used for the removal of a succession of bound booklets from a supply hopper which is adapted to hold a stack of the booklets and for the feeding of the booklets to a subsequent apparatus for further processing. The machine includes a reciprocating vacuum feed plate, and first and second stage separating mechanism. The reciprocating vacuum feed plate is disposed in the bottom of the hopper which is used for advancing the bottom booklet through a discharge opening to a take away feed mechanism. When the machine is in use, the first and second stage separating mechanism initially maintains at least the bottom two booklets in the hopper in a shingled relationship such that a marginal portion of the adjacent bound booklet is exposed. A pressing member is then applied to maintain a normal force on the exposed marginal portion of the bottom booklet so as to prevent it from wrinkling and becoming jammed in the discharge opening when the vacuum feed plate is moving the booklet toward the discharge opening. The second stage separating separator then further ensures that only one booklet at a time can pass through the discharge opening.
In U.S. Pat. No. 4,030,722 issued to IRVINE et al. on Jun. 21, 1977, a sheet-material separator and feeder system is taught. The sheet-material separating and feeding system is used for the handling of a wide range of sheet thicknesses and sizes at high speed. Further, the system does not require on-going adjustments or a pre-sorting of materials. When in use, the sheets are stacked at one end of the system, and are then fed to a first of two separator mechanisms. The first separator mechanism is adjusted for thicker sheets of the range. Sheets leaving the first separator are subsequently fed to the second of the two separator mechanisms. The second separator is adjusted for thinner sheets of the range. Sheets leaving the second separator are ejected one at a time. The ejected sheets can be fed to other sheet handling equipment for processing. Generally, the sheet-material separator and feeder system as taught in this patent is directed for sheet-like materials such as envelopes, letters and pieces of mail.
In U.S. Pat. No. 5,769,408 issued to SELAK et al. on Jun. 23, 1998, an apparatus for feeding sheets is taught. In particular, the patent teaches a system for feeding a stack of sheets at a high rate of speed which prevents the sheets from bottlenecking or jamming in the sheet feeder. The sheet feeder includes a platform supporting a stack of sheets, feed rollers and downstream pull rollers, and first and second sensors. The first sensor detects the sheet and controls the on/off driving mechanism for the feed rollers. The second sensor detects the sheet and controls the on/off driving mechanism for the pull rollers. When in use, the feed roller section moves the sheets one at a time to the pull roller section.
Finally, in U.S. Pat. No: 4,982,942 issued to KONISHI et al. on Jan. 8, 1991, a sheet feed mechanism is taught. In particular, the sheet feed mechanism is used for feeding sheets one at a time. The mechanism comprises a hopper loaded with a stack of sheets, a feed roller disposed near the outlet of the hopper, and a resilient tongue which is held in resilient contact with the central section of the feed roller. The central section of the feed roller is provided with an alternate circumferential arrangement of low friction and high friction portions. The feed roller is designed such that the friction coefficients between the sheet and the low friction portions is smaller than that between the sheet and the tongue, and the friction coefficient between the sheet and the high friction portions is greater than that between the sheet and the tongue.
It will be apparent from the foregoing prior art that the initial height of the stack of documents at the loading end of the dispenser in some instances is limited, especially for dispensers which employ a bottom feed mechanism.